Silane and borane treatments for titanium carbide films

ABSTRACT

Methods of treating metal-containing thin films, such as films comprising titanium carbide, with a silane/borane agent are provided. In some embodiments a film comprising titanium carbide is deposited on a substrate by an atomic layer deposition (ALD) process. The process may include a plurality of deposition cycles involving alternating and sequential pulses of a first source chemical that comprises titanium and at least one halide ligand, a second source chemical comprising metal and carbon, wherein the metal and the carbon from the second source chemical are incorporated into the thin film, and a third source chemical, wherein the third source chemical is a silane or borane that at least partially reduces oxidized portions of the titanium carbide layer formed by the first and second source chemicals. In some embodiments treatment forms a capping layer on the metal carbide film.

REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. application Ser. No.14/461,995 filed Aug. 18, 2014, which is a continuation of U.S.application Ser. No. 13/829,856 filed Mar. 14, 2013 and issued as U.S.Pat. No. 8,841,182, each of which is hereby incorporated by reference inits entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to processes for producing metalcarbide thin films on a substrate by atomic layer deposition. In someembodiments, titanium carbide films produced by the atomic layerdeposition (ALD) processes disclosed herein can be used in metal gateand metal electrode applications in metal oxide semiconductor fieldeffect transistors (MOSFETs), such as n-channel MOSFETs (NMOS).

2. Description of the Related Art

Atomic layer deposition (ALD) is a generally self-limiting process,whereby alternated pulses of reaction precursors saturate a substratesurface and leave no more than about one monolayer of material perpulse. The deposition conditions and precursors are selected to provideself-saturating reactions, such that an adsorbed layer in one pulseleaves a surface termination that is non-reactive with the gas phasereactants of the same pulse. A subsequent pulse of different reactantsreacts with the previous termination to enable continued deposition.Thus, each cycle of alternated pulses leaves no more than about onemolecular layer of the desired material. The principles of ALD typeprocesses have been presented by T. Suntola, e.g. in the Handbook ofCrystal Growth 3, Thin Films and Epitaxy, Part B: Growth Mechanisms andDynamics, Chapter 14, Atomic Layer Epitaxy, pp. 601-663, ElsevierScience B.V. 1994, the disclosure of which is incorporated herein byreference.

In a typical ALD process for depositing thin films, one deposition cyclecomprises exposing the substrate to a first precursor, removingunreacted first reactant and reaction byproducts from the reactionchamber, exposing the substrate to a second precursor, followed by asecond removal step. Typically, halide precursors, such as TiCl₄ andHfCl₄, are used as precursors in ALD deposition because those precursorsare inexpensive and relatively stable, but at the same time reactivetowards different types of surface groups. H₂O and NH₃ are widely usedfor oxide and nitride deposition, respectively, as second precursors.

ALD processes typically produce thin films that have lower impuritycontent at the same deposition temperature than chemical vapordeposition (CVD) processes. Despite the lower impurity levels in ALDfilms, the impurity content in ALD films can still be a problem. Thereare several possible reasons for the presence of impurities in thinfilms deposited by ALD. In some cases, the semiconductor process flownecessarily limits the maximum deposition temperature such that thatsome residues are left in the film. ALD films deposited from chloride orother halide-containing precursors (e.g., WF₆) at relatively lowtemperatures can comprise relatively high levels of halide residues.Halide impurities are present mainly at the interfaces, which can alsolead to problems. In some cases, like low temperature deposition oftransition metal nitrides and transition metal carbides from halidecontaining precursors, the impurity contents can be above the acceptablelimit for some integrated circuit (IC) applications. In another example,in some applications amorphous films are needed, which limits the growthtemperature.

In some ALD processes a deposited layer comprising Ti, Al, and C can beundesirably oxidized by contaminants such as water and air. In NMOSapplications, oxidation of such a layer or thin film may lead to a shiftin the workfunction, for example, from N-type to P-type.

SUMMARY OF THE INVENTION

According to some embodiments of the invention, an organosilane,organoborane, silane, or borane (generally referred to herein as a“silane/borane agent”) is utilized in atomic layer deposition (ALD)processes for depositing a boron- or silicon-containing film comprisingmetal carbide from a halide-containing precursor or in treating adeposited film that comprises metal carbide. The silane/borane agent maybe pulsed during or after a deposition cycle, or it may be applied to athin film after some or all cycles have been completed. In someembodiments, the silane/borane agent may serve to reduce oxidizedportions of a metal film. In some embodiments, the silane/borane agentmay form a barrier to at least partially prevent further oxidation ofthe film itself or of films subsequently deposited over the treatedfilm. In some embodiments, the silane/borane agent may help in getteringoxygen from deeper within a film, such as oxygen coming from subsequentair exposure.

In some embodiments, the silane/borane treatment may form a cappinglayer comprising silicon or boron. In some embodiments the capping layermay comprise a portion of the metal carbide layer that comprises siliconor boron. In some embodiments the capping layer is formed directly onthe metal carbide layer. In some embodiments the capping layer comprisesa portion of the metal carbide film comprising silicon or boron as wellas a layer comprising silicon or boron formed on the metal carbidelayer.

In some cases, the barrier effect of the silane/borane agent treatmentmay also prevent or limit oxidation of one or more layers depositedafter the silane/borane treatment of the metal carbide film. Forexample, the use of a silane/borane agent in the formation or treatmentof a metal carbide film, such as a titanium carbide film, may limitoxidation of a second film deposited over the titanium carbide film,such as a nitride film (for example TiN) even if the second film is notitself treated with a silane/borane agent. Additional subsequentlydeposited films may also be protected from oxidation by thesilane/borane agent treatment of the metal carbide layer.

In some embodiments, however, additional films deposited after the metalcarbide, such as a titanium nitride film, a hafnium oxide film, asilicon or silicon oxide film, or a tungsten film, are themselvestreated with a silane/borane agent to achieve at least some of theadvantages enjoyed by the treated metal carbide films.

The duration of the silane/borane agent exposure can be controlled toachieve a desired result. For example, the duration of exposure can bebased on a desired level of interaction with the metal film and thedesired depth of diffusion or penetration into the film. In someembodiments the duration of the exposure is controlled to form a cappinglayer of a desired thickness and/or composition.

In some embodiments, the silane/borane is selected from the groupconsisting of organosilanes and organoboranes, monosilane, disilane,trisilane, borane, diborane, and triborane. The silane/borane agent maybe provided in each ALD cycle, at intervals during the depositionprocess, or after the completion of some or all of the cycles. In someembodiments, the silane/borane agent may be provided to the substrate invapor form. In some embodiments the silane/borane agent, such astrisilane, may be applied to the substrate in liquid form.

In some embodiments, ALD processes for forming a titanium-carbide thinfilm are disclosed. The processes may comprise contacting a substrate ina reaction space with alternating and sequential pulses of a titaniumsource chemical that comprises at least one halide ligand, a secondsource chemical comprising a metal and carbon and a third sourcechemical, wherein the third source chemical is a silane/borane. Asdiscussed in more detail below, the third source chemical may be appliedas a part of each deposition cycle, as a part of only some cycles, orafter all the cycles have been completed. The second source chemical maycomprise an organic ligand, and in some embodiments may be TMA(trimethylaluminum) or TEA (triethylaluminum). In some embodiments, thesecond source chemical is dimethylaluminumhydride DMAH ortris(tertbutyl)aluminum TTBA.

In some embodiments, ALD processes for forming a titanium carbide filmare disclosed, in which alternating and self-saturating pulses ofreactants are provided in a plurality of deposition cycles. Each cyclepreferably comprises contacting a substrate in a reaction space withalternating and sequential pulses of a titanium source chemical,preferably a titanium halide compound, a carbon source chemical, and asilane or borane source chemical. The silane or borane source chemicalcan be selected from monosilane, disilane, trisilane, borane, anddiborane, organosilane and organoborane, and in one embodiment istrisilane.

In yet another aspect of the invention, a semiconductor device structureis disclosed. The structure comprises a substrate and a thin film layeroverlying the substrate, wherein the thin film layer is formed by ALD bycontacting the substrate with alternating and sequential pulses of ametal source chemical, a carbon source chemical, and a silane/boraneagent.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be better understood from the Detailed Description ofthe Preferred Embodiments and from the appended drawings, which aremeant to illustrate and not to limit the invention, and wherein:

FIG. 1 is a flow chart generally illustrating a method of forming abinary compound by ALD, in which supply of a silane/borane agent followsremoval of excess second reactant and by-products, in accordance withsome embodiments of the invention;

FIG. 2 is a schematic cross-sectional side view of a electrodestructure, comprising a layer of a conductive metal carbide, accordingto some embodiments of the invention; and

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The present disclosure provides atomic layer deposition (ALD) methodsfor forming metal carbide thin films, such as titanium carbide thinfilms. Although described primarily in terms of titanium carbide thinfilms, other types of thin films may be deposited and/or treated withthe disclosed methods, such as niobium carbide films, as discussed inmore detail below.

The ALD methods may comprise exposing the films to silane or borane toreduce or substantially prevent oxidation of the titanium carbide filmand the accompanying buildup of oxygen at the interface of the titaniumcarbide film and an overlying layer as well as diffusion of possibleoxygen beyond the interface between a titanium carbide film and anunderlying layer. As mentioned above, such a buildup of oxidation cancause a shift in the workfunction of the thin film. In some embodiments,a silane or borane treatment can be used to reduce the resistivity of athin titanium carbide film. The silane or borane may be provided duringeach titanium carbide deposition cycle, after a certain number oftitanium carbide deposition cycles, or after all the titanium carbidedeposition cycles have been completed. In some preferred embodiments,the silane or borane agent is a borane or an organoborane, such asdiborane, or a silane or organosilate, such as silane, disilane, ortrisilane.

DEFINITIONS

As used in this disclosure, the term “ALD process” is used in accordancewith its ordinary meaning in this field and includes a process forproducing thin films over a substrate in which a thin film is formedmolecular layer by molecular layer due to self-saturating chemicalreactions. The general principles of ALD are disclosed, for example, inU.S. Pat. Nos. 4,058,430 and 5,711,811, the disclosures of which areincorporated herein by reference. In an ALD process, gaseous reactants,i.e., precursors, are conducted into a reaction chamber of an ALD typereactor where they contact a substrate located in the chamber to providea surface reaction. The pressure and the temperature of the reactionchamber are adjusted to a range where physisorption (i.e. physicaladsorption or condensation of gases) and thermal decomposition of theprecursors are avoided. Consequently, only up to about one monolayer(i.e. an atomic layer or a molecular layer) of material is deposited ata time during each pulsing cycle. The actual growth rate of the thinfilm, which is typically presented as A/pulsing cycle, depends, forexample, on the number of available reactive surface sites or activesites on the surface and bulkiness of the chemisorbing molecules. Gasphase reactions between precursors and any undesired reactions ofby-products are inhibited because precursor pulses are separated fromeach other by time and the reaction chamber is purged with an inactivegas (e.g. nitrogen or argon) and/or evacuated using, e.g., a pumpbetween precursor pulses to remove surplus gaseous reactants andreaction by-products from the chamber.

As used in this disclosure, the term “reaction space” is used inaccordance with its ordinary meaning in this field and includes areactor or reaction chamber, or an arbitrarily defined volume therein,in which conditions can be adjusted to effect thin film growth by ALD.Typically the reaction space includes surfaces subject to all reactiongas pulses from which gases or particles can flow to the substrate, byentrained flow or diffusion, during normal operation. The reaction spacecan be, for example, in a single-wafer ALD reactor or a batch ALDreactor, where deposition on multiple substrates takes place at the sametime.

As used in this disclosure, the term “adsorption” is used in accordancewith its ordinary meaning in this field and includes a chemicalattachment of atoms or molecules on a surface.

As used in this disclosure, the term “soak” describes exposing a thinfilm, such as a titanium carbide film, to a chemical such as asilane/borane agent for a period of about 10 seconds to about 600seconds, preferably from about 30 seconds to about 300 seconds and morepreferably from about 45 seconds to about 180 seconds. In some cases,the duration of a soak is longer than the duration of a pulse oftitanium or carbon reactants in an ALD cycle. The duration of a soak maybe adjusted to obtain a desired amount of silicon in a metal carbidefilm. For example the duration of the soak can be adjusted to determinea penetration depth or the extent of diffusion in the metal carbidefilm. In some embodiments the Si does not necessarily penetrate into thefilm, as its presence on the surface of the film may serve as an oxygenor oxidation barrier (or nitrogen barrier, for example where asubsequent layer such as a TiN is deposited on the treated film).

As used in this disclosure, the term “thin film” is used in accordancewith its ordinary meaning in this field and includes a film that isgrown from elements or compounds that are transported as separate ions,atoms or molecules via vacuum, gaseous phase or liquid phase from thesource to the substrate. The thickness of the film depends upon theapplication and may vary in a wide range, preferably from one atomiclayer to 1,000 nm or more. In some embodiments, the thin film is lessthan about 20 nm in thickness, even more preferably less than about 10nm and most preferably less than about 5 nm or less than about 3 nm.

Subscripts “x” and “y” are used to designate species that are notnecessarily stoichiometric, having a wide range of phases with varyingmetal/oxygen, metal/carbon, metal/nitrogen, or metal/carbon/nitrogenratios.

ALD Methods

The methods presented herein allow deposition of conformal metal carbidethin films on substrate surfaces. In some embodiments, thin films aredeposited from halogen-containing chemicals. Geometrically challengingapplications are also possible due to the self-limited nature of thesurface reactions in ALD processes.

According to some embodiments, an ALD type process is used to formtitanium carbide thin films on substrates, such as integrated circuitworkpieces. The surfaces on which the thin titanium carbide (TiC) filmsare deposited can take a variety of forms. Examples include, but are notlimited to, silicon, silicon oxide (SiO₂), coated silicon, dielectricmaterials, low-k materials, metals—such as copper and aluminum—metalalloys, metal oxides and various nitrides, such as transition metalnitrides and silicon nitride or a combination of said materials. In someembodiments, the substrate comprises titanium nitride. In someembodiments, the substrate comprises hafnium oxide.

In a some embodiments, a substrate or workpiece is placed in a reactionchamber and subjected to alternately repeated surface reactions. Inparticular, thin films are formed by repetition of an ALD cycle. EachALD cycle is typically self-limiting. In the case of compound metallicthin film deposition, at least two different source chemicals arealternatively employed. One reactant will form no more than about onemonolayer on the substrate surface and includes a metal species desiredin the layer being deposited. This reactant, also referred to herein as“the metal reactant,” is preferably a titanium halide, such as TiCl₄, ora niobium halide, such as NbCl₅, and thus the deposited monolayer isterminated with halogen ligands.

A second reactant preferably contributes carbon to the growing film. Insome embodiments, the second reactant comprises a metal and carbon, suchas TMA or TEA. In some embodiments, the second reactant is ametal-containing source chemical comprising at least one ligand, such asa metalorganic compound. Further, in some embodiments the secondreactant can also leave some amount of metal in the film beingdeposited. For example, in the case of TMA or TEA, some amount ofaluminum may be left in the film, depending on the particular reactionconditions. In some embodiments, the formation of an aluminum carbide inthe form of Al_(x)C_(y) may also provide protection against oxidation.

In some embodiments according to the present disclosure, a thirdreactant is provided every cycle, after a certain number of cycles, orafter deposition of the metal carbide film is complete. The thirdreactant may be a silicon compound, or a boron compound, preferably onethat is a strong reducer. In some embodiments the third reactantcomprises a silane/borane agent. The silane/borane agent is morereactive to oxygen than is the metal of the metal carbide film, forexample titanium and/or niobium, and thus is capable of reducing theamount of metal oxide in the film. In some cases, little or no oxygen isactually removed from the thin film; however, the silane/borane agentacts to reduce metal oxide, such as titanium oxide by breaking the bondsbetween titanium and oxygen to return the titanium to its pure titaniumcarbide form. In such cases, although, the oxygen has not actually beenremoved from the film, it is bound up by the silane/borane agent so asto not impede the workfunction of the thin film. Accordingly, it couldalso be said that application of a silane/borane agent increases theamount of TiC compared to the amount of TiOC in the film. Moreover, insome embodiments the third reactant also provides a species desired inthe thin film, such as silicon, boron, or carbon. However, it should bementioned that in some embodiments, there will be little or no oxygenfor the silane/borane agent to bond with during the deposition process.In such cases, the silicon or boron deposited with the TiC thin film mayact as a barrier to oxygen if and when the TiC film is exposed tooxygen, such as when a workpiece is moved from one chamber to another.For example, treatment of a titanium carbide layer during deposition mayreduce or prevent oxidation of the titanium carbide layer when it ismoved to another reactor for further processing, such as deposition ofan overlying titanium nitride layer.

The silane/borane agent may be selected from the group consisting ofmonosilane, disilane, trisilane, organosilanes, borane, diborane,organoboranes, or any other suitable material that readily reacts withoxygen to reduce titanium, niobium or other metal in the metal carbide.The silane/borane agent may be supplied in vapor or liquid form, and maybe applied as a relatively short pulse every cycle or intermittently inthe deposition process or as a relatively longer soak to a partially orcompletely formed titanium carbide layer.

The silane/borane agent may be provided in each ALD cycle, at intervalsduring the deposition process, or after the deposition process has beencompleted. For example, in some embodiments the silane/borane agent isprovided every one to four ALD cycles. In some embodiments, at the timethe silane/borane agent is provided, the film grown in the most recentALD cycles is preferably thin enough that the silane/borane agent canpenetrate the film. In some embodiments, such as situations where morethan one deposition cycle has been completed prior to exposure to thesilane/borane agent, the amount of silane/borane penetration in thefilms can be controlled by the quantity or concentration of the agentused or the duration of the exposure.

The silane/borane agent may be provided as a part of one or more cyclesor may be applied after one or more cycles have been completed. Thus, insome embodiments, the deposition of a metal carbide film, such as TiC,is considered to be a cycle in an ALD process independent of theapplication of a silane/borane agent. In such cases, the cycle isrepeated as many times as desired, and the silane/borane treatment isapplied after some or all of the cycles. However, in some embodiments,the silane/borane agent is applied during one or more cycles (as a partof an ALD cycle) as well as after one or more cycles (separate from anALD cycle).

In one phase of an ALD cycle (“the metal phase”, for example “thetitanium phase” or the “first phase”), the reactant or source chemicalcomprising titanium (or other metal such as niobium) is supplied to thereaction chamber and chemisorbs to the substrate surface. The reactantsupplied in this phase is selected such that, under the preferredconditions, the amount of reactant that can be bound to the surface isdetermined by the number of available binding sites and by the physicalsize of the chemisorbed species (including ligands). The chemisorbedlayer left by a pulse of the titanium reactant is self-terminated with asurface that is non-reactive with the remaining chemistry of that pulse.This phenomenon is referred to herein as “self-saturation.” One of skillin the art will recognize that the self-limiting nature of this phasemakes the entire ALD cycle self-limiting. Excess reactant and reactantbyproducts (if any) are removed from the reaction space, for example bypurging with an inert gas and/or evacuation.

Maximum step coverage and conformality on the workpiece surface isobtained when no more than about a single molecular layer of metalsource chemical molecules is chemisorbed in each self-limiting pulse.Due to the size of the chemisorbed species and the number of reactivesites, somewhat less than a monolayer may be deposited in each pulse ofmetal reactant. However, the use of some reactants, such as TEA or TMA,may result in more than a monolayer because they may at least partiallyself-decompose at the deposition temperature. The degree ofself-decomposition can be a function of pulse time.

In the next phase of the cycle, a pulse of a second source chemical isprovided that reacts with the molecules left on the substrate surface bythe preceding pulse. In some embodiments the source chemical preferablycomprises carbon that is to be incorporated in the thin film. The carbonis incorporated into the thin film by the interaction of the sourcechemical with the monolayer left by the metal reactant. This phase isreferred to herein as “the second phase” or the “carbon-contributingphase.” In some embodiments, the second source chemical is a carboncontaining compound and its reaction with the chemisorbed metal speciesproduces a metal carbide layer on the substrate. In some embodiments thesecond source chemical also comprises a second metal, such as aluminum,and the second metal is incorporated into the growing film along withthe carbon. In some embodiments the species-contributing source chemicalcomprises metal and carbon and may be, for example, TMA or TEA.

Excess second source chemical and reaction byproducts, if any, areremoved from the reaction space by purging and/or evacuation.

In some embodiments, a third phase of the ALD cycle comprises providingthe silane/borane agent. The silane/borane agent may comprise a speciesthat may be incorporated into the thin film, such as boron or silicon.This is referred to as the “third phase” or the “oxygen isolationphase.”

Although referred to as the “first phase,” the “second phase” and the“third phase,” these labels are for convenience and do not indicate theactual order of the phases in each ALD cycle. Thus, the initial ALDcycle may be started with any of the three phases described above.However, one of skill in the art will recognize that if the initial ALDcycle does not begin with the metal reactant phase, at least two ALDcycles will typically need to be completed to deposit about a monolayerof the desired metal carbide thin film.

In addition, the order of the phases may be changed. That is, in someembodiments the silane/borane agent may be the next reactant providedafter the second reactant, while in other embodiments the silane/boraneagent may be the next reactant provided after the first metal sourcereactant. And in some embodiments, the silane/borane agent may besupplied after only some cycles or after all cycles have been completed.For example, in some embodiments the third phase (provision of thesilane/borane agent) may immediately follow the first phase (provisionof the reactant comprising a metal species), which in turn is followedby the carbon-contributing phase. And in some embodiments, the thirdphase may be supplied as a vapor “soak” after the thin film has beencompletely formed. That is, the deposited film is exposed to a silane ora borane in vapor form for a period of time. A phase is generallyconsidered to immediately follow another phase if only a purge or otherreactant removal step intervenes.

In some embodiments the silane/borane agent is not provided in every ALDcycle. Rather, a partially or completely deposited titanium carbide filmmay be treated with a silane/borane agent. This may be the case, forexample, where a first film has been formed using TiCl₄ and TEA but theresulting TiAlC film has been oxidized by water, air, or some othercontaminant source to form a layer that is essentially TiAlOC. Asilane/borane agent can be applied to the first film which may reducethe TiAlOC layer back to essentially TiAlC with only the minor presenceof impurities.

In one embodiment, an ALD cycle comprises:

-   -   1. providing a titanium halide to the reaction space;    -   2. substantially purging and/or evacuation of excess titanium        halide and reaction byproducts;    -   3. providing a carbon-contributing reactant to the reaction        space, such TEA or TMA;    -   4. substantially purging and/or evacuation of excess second        reactant and reaction byproducts; and    -   5. providing a silane/borane agent to the reaction space.

Step 5 can be included in each ALD cycle, or steps 1-4 can be repeatedseveral times before step 5 is introduced. In some embodiments steps 1-4are repeated up to 10 times before step 5 is included. In otherembodiments steps 1-4 are repeated up to 100 or even 1000 or more timesbefore step 5 is included. In some embodiments, a complete film ofdesired thickness is deposited prior to step 5.

With reference to FIG. 1, in an embodiment of the invention, afterinitial surface termination, if necessary, a first reactant or sourcechemical pulse is supplied 102 to the substrate or workpiece. In theillustrated embodiment, the first reactant is a metal halide, and thethin film being formed comprises a metal carbide. In accordance with apreferred embodiment, the first reactant pulse comprises a carrier gasflow and a volatile titanium halide species that is reactive with theworkpiece surfaces of interest. Accordingly, the halogen-containingtitanium species adsorbs upon the workpiece surfaces. The first reactantpulse self-saturates the workpiece surfaces such that any excessconstituents of the first reactant pulse do not further react with themonolayer formed by this process. Self-saturation results due to halidetails terminating the monolayer, protecting the layer from furtherreaction.

The first reactant is then removed 104 from the reaction space. Step 104may entail merely stopping the flow of the first reactant or chemistrywhile continuing to flow a carrier gas for a sufficient time to diffuseor purge excess reactants and reactant by-products from the reactionspace. Preferably the removal 104 comprises continuing to flow purge gasfor between about 0.1 seconds and 20 seconds after stopping the flow ofthe first reactant pulse. Inter-pulse purging is described in co-pendingU.S. Pat. No. 6,511,539, entitled “IMPROVED APPARATUS AND METHOD FORGROWTH OF A THIN FILM,” the disclosure of which is incorporated hereinby reference. In other arrangements, the chamber may be pumped downbetween alternating chemistries. See, for example, PCT publicationnumber WO 96/17107, published Jun. 6, 1996, entitled “METHOD ANDAPPARATUS FOR GROWING THIN FILMS,” the disclosure of which isincorporated herein by reference. Together, the adsorption 102 andreactant removal 104 represent a first phase 105 in an ALD cycle. Thefirst phase in the illustrated ALD cycle is thus the metal phase.

With continued reference to FIG. 1, a second reactant or source chemicalpulse is then supplied 106 to the workpiece. The second chemical reactswith the monolayer left by the first reactant. In the illustratedembodiment, this second reactant pulse 106 comprises supplying a carriergas with the second source gas to the workpiece. In particular, wherethe first reactant comprises a titanium halide, the second reactant,such as TMA or TEA, comprises carbon and a second, different metal. Inthe case of TEA or TMA the second reactant leaves no more than about amonolayer of TiAlC. The second reactant preferably removes at least somehalide ligands from the adsorbed first reactant. The second reactantpulse 106 also leaves a surface termination that operates to limit thedeposition in a saturative reaction phase.

After a time period sufficient to completely saturate and react themonolayer with the second reactant pulse 106, any excess second reactantis removed 108 from the workpiece. As with the removal 104 of the firstreactant, this step 108 may comprise stopping the flow of the secondchemistry and continuing to flow carrier gas for a time periodsufficient for excess reactants and volatile reaction by-products fromthe second reactant pulse to diffuse out of and be purged from thereaction space. Together, the second reactant pulse 106 and removal 108represent a second phase 109 in the illustrated process, and can also beconsidered a carbon and metal species-contributing phase.

When the excess reactants of the second reactant pulse have been removed108 from the chamber, a third reactant or source chemical pulse may besupplied to the workpiece 110. The third reactant can be a silane/boraneagent capable of removing halides and/or reacting with oxygen in thegrowing film. Examples of suitable silanes and boranes includemonosilane, disilane, trisilane, borane, and diborane. The silane/boraneagent may be provided with an inert carrier gas. Temperature andpressure conditions can be adjusted to control the level of diffusion ofthe silane/borane agent through the monolayer.

After a time period sufficient to achieve a desired level of saturationof the third reactant in the monolayer, excess unreacted silane/boraneagent and any reaction by-products (which may also be volatile) areremoved 112 from the reaction space, for example by a purge gas pulse.The removal can be as described for step 104. Together, thesilane/borane agent pulse 110 and removal 112 represent a third phase113 of the illustrated ALD process, which can also be referred to as theoxygen isolation phase.

In some embodiments, supply of silane/borane agent immediately followsthe step of removing excess first reactant and by-products. After a timeperiod sufficient to react the monolayer with the silane/borane agent,excess unreacted silane/borane agent and reaction by-products areremoved from the reaction space, possibly by a purge gas pulse. Theremoval step is followed by supply of the second reactant pulse.

In some embodiments of the disclosure (not shown), the steps ofsupplying the silane/borane agent and removing any excess silane/boraneagent and by-products precede the step of supplying the first reactant.In some embodiments, the silane/borane agent is not provided in everycycle or may be provided after all the cycles are complete.

In some embodiments, the step of supplying a silane/borane agent takethe form of a soak occurring after some or all of the titanium carbidedeposition cycles have been completed. In some cases, a soak oftrisilane occurring after deposition of a TiC film is completed has beenfound to achieve suitable results.

In one embodiment, a process for forming a titanium carbide filmcomprises:

-   -   1. providing a titanium halide, such as a titanium chloride, to        the reaction space;    -   2. substantially purging and/or evacuation of excess titanium        halide and reaction byproducts;    -   3. providing a second carbon and aluminum-contributing reactant,        such as TEA or TMA, to the reaction space;    -   4. substantially purging and/or evacuation of excess second        reactant and reaction byproducts;    -   5. repeating steps 1 through 4 for either a desired number of        cycles or until a film of a desired thickness has been achieved;        and    -   6. soaking the product of step 5 with a silane/borane agent

In some embodiments the soak of Step 6 can be configured to achieve aparticular level of interaction between any oxygen present in the filmand the silane/borane agent. In some embodiments the soak of Step 6 canbe configured to provide a desired amount of silicon or boron in thefilm to a particular depth. For example, the soak may last long enoughto allow silicon or boron to substantially diffuse throughout the filmor the soak's duration may be kept shorter so as to reach only a partialdepth in the film. The duration of the soak may be from about 5 secondsto about 600 seconds, preferably from about 10 seconds to about 180seconds, more preferably from about 20 seconds to about 120 seconds andin some embodiments from about 30 seconds to about 60 seconds. In somecases, such as batch processes, the soaking time might be even longer.In some such embodiments, the soak is performed for about 30 seconds toabout 600 seconds, preferably from about 45 seconds to about 180seconds, more preferably from about 60 seconds to about 120 seconds.

In some embodiments, a soak may serve to “cap” a thin film with anoxygen barrier by providing silicon or boron in a portion of the film oron the film itself. In some embodiments, a deposited or partiallydeposited metal carbide layer is soaked in a silane/borane agent, suchas disilane or trisilane, to form a thin “capping” layer having athickness below about 3 nm, more preferably below about 2 nm and mostpreferably below about 1 nm. Formation of a capping layer in the initialphase of the soak may stop the diffusion of silicon or boron into thefilm while still having a beneficial effect on the surface of the film.

According to some embodiments, the capping layer is a separate layercomprising silicon or boron and formed directly on the thin film. Insome embodiments, the capping layer may also or alternatively comprise aportion of the metal carbide layer, or whatever layer it is applied to,where that portion comprises silicon or boron from the treatment withthe silane or borane agent. The nature of the capping layer may depend,for example, on the treatment conditions and/or the silane/borane agentthat is used. Where the capping layer comprises a portion of theunderlying metal layer, such as a metal carbide layer, there may be agradient within the underlying layer with a greater concentration of thesilicon or boron toward the top of the layer and a decreasingconcentration at increased depths from the top of the layer. Thegradient—both the depth to which the silane/borane agent extends as wellas the concentration at any given depth—may depend, in part on thetreatment conditions (duration, temperature, pressure, etc.) and theparticular silane/borane agent used. According to some embodiments, thesilane/borane agent may at least partially react with the underlyinglayer. In some cases, the capping layer may comprise a layer comprisingsilicon or boron formed directly on the underlying film as well as aportion of the film in which silicon or boron is present. In someembodiments the capping layer is a silicon or boron layer formeddirectly over and contacting a metal carbide layer, such as a TiC layer.

According to some embodiments, the reaction temperature may be fromabout 300° C. to about 500° C., preferably from about 325° C. to about450° C., and more preferably from about 350° C. to about 450° C.

The foregoing embodiments will be discussed in the context of specificthin film chemistries.

Deposition of Carbon-Containing Films

Carbon containing metal films or metal carbides have varyingapplications, such as gate electrodes, electrodes in capacitors andbarrier layers in damascene and dual damascene structures.

In some embodiments, a general pulsing sequence for carbon-containingmetal or metal carbide thin film deposition is:

(M¹X_(y)+purge+M²R₃+purge+silane/borane agent+purge)×m₁

or

(M¹X_(y)+purge+silane/borane agent+purge+M²R₃+purge)×m₁,

-   -   wherein m₁ is the number of total cycles. M¹ is a metal atom,        preferably selected from the group consisting of Ti, Zr, Hf, V,        Nb, Ta, Cr, Mo, W.

M² is a metal atom, preferably selected from the group consisting of B,Al, In, Bi, Sn, Zn, Pb, Sb and Ga. R is a ligand for M² and can be anyligand, preferably a metalorganic ligand, more preferably anorganometallic ligand, most preferably an alkane ligand, such as ethylligand.

X_(y) is one or more ligands for M¹. Each X may be a halogen ligandselected from the group consisting of I, Br, Cl and F. However, in someembodiments at least one X can be a metalorganic ligand, such as acyclopentadienyl (for example, cyclopentadienyl, methylcyclopentadienyl,pentamethylcyclopentadienyl, ethylcyclopentadienyl,isopropylcyclopentadienyl, tertbutylcyclopentadienyl, and indenyl),alkyl (for example, methyl, ethyl, propyl, and butyl), carbonyl,cyclo-octadiene, benzene or hydrogen ligand. In other embodiments X_(y)may comprise mixtures thereof. However, at least one of the X_(y)ligands is preferably a halogen. As an example,bis(cyclopentadienyl)hafnium dichloride orbis(cyclopentadienyl)tantalum(V) trichloride, can be used as a metalprecursor in some embodiments. In some embodiments no X is oxygen ornitrogen.

The silane/borane agent may be selected from the group consisting ofmonosilane, disilane, trisilane, borane, and diborane. In someembodiments, the silane/borane agent is a disilane or a trisilane thatis applied during or after each layer is deposited, after only somelayers are deposited, or after all the layers have been deposited. Thesilane/borane agent can be applied in a pulse or as a soak and as aliquid or a vapor.

In preferred embodiments, M² is a metal, preferably aluminum, and R is acarbon-containing ligand. M²R₃ preferably has at least onemetal-to-carbon bond. In some embodiments, M²R₃ may be considered acarbon source chemical. In some embodiments, M²R₃ is selected from thegroup consisting of TMA and TEA. In some embodiments M²R₃ is DMAH. Insome embodiments M²R₃ is TTBA.

One benefit of the ALD processes of some embodiments is that the growthrate is extremely high for an ALD process. For example, the growth ratefor TaC formation can be over 2 Å/cycle. Further, annealing can beperformed after the metal carbide deposition for enhancing theproperties of the film. Suitable atmospheres, such as N₂ or forming gas(N₂/H₂), may be used during annealing.

Exemplary pulsing sequences for TiC film formation include:

(TiCl₄+purge+trimethylaluminum (TMA) or triethylaluminum(TEA)+purge+silane/borane agent+purge)]×m₂

and

(TiCl₄+purge+silane/borane agent+purge+TMA or TEA+purge)]×m₂,

-   -   wherein m₂ is the number of total cycles and the silane/borane        agent is selected from the group consisting of monosilane,        disilane, trisilane, borane, and diborane.

Films deposited using the above exemplary pulsing sequence contained,based on an atomic basis, about 17-20% Ti, about 17-27% Al, about 16-42%Si, and about 21-39% C. These values were determined using Rutherfordbackscattering spectrometry, or RBS.

In other embodiments, a silane/borane agent is not utilized every cyclebut only in some of the cycles. In this situation, a general pulsingsequence for carbon-containing metal thin film deposition can be:

[n₃×(M¹X_(y)+purge+M²R₃+purge)+m₃×(silane/borane agent+purge)]×k₃,

wherein n₃ is the number of carbide cycles in one total cycle, m₃ is thenumber of cycles in which a silane/borane agent is used in one totalcycle, and k₃ is the number of total cycles. M¹ is preferably Ti but maybe a metal atom selected from the group consisting of Zr, Hf, V, Nb, Ta,Cr, Mo, and W. M² is preferably Al but may be a metal atom selected fromthe group consisting of B, Al, In, Sn, Bi, Zn, Pb, Sb and Ga. R is aligand for M² and can be any ligand.

X_(y) is one or more ligands for M¹. Each X is preferably a halogenligand selected from the group consisting of I, Br, Cl and F. However,in some embodiments at least one X can be a metalorganic ligand, such asa cyclopentadienyl (for example, cyclopentadienyl,methylcyclopentadienyl, pentamethylcyclopentadienyl,ethylcyclopentadienyl, isopropylcyclopentadienyl,tertbutylcyclopentadienyl, and indenyl), alkyl (for example, methyl,ethyl, propyl, and butyl), carbonyl, cyclo-octadiene, benzene orhydrogen ligand. In other embodiments X_(y) may comprise mixturesthereof. However, at least one of the X_(y) ligands is preferably ahalogen. As an example, bis(cyclopentadienyl)hafnium dichloride orbis(cyclopentadienyl)tantalum(V) trichloride, can be used as a metalprecursor in some embodiments. In some embodiments no X comprisesnitrogen or oxygen.

According to some embodiments, the reaction temperature may be fromabout 300° C. to about 500° C., preferably from about 325° C. to about450° C., and more preferably from about 350° C. to about 450° C.

The exact composition of a thin film produced using the methods andmaterials disclosed herein may vary. Titanium carbide films fabricatedaccording to the present disclosure may contain a number of differingelemental components including, but not limited to titanium, aluminum,carbon, silicon and/or boron depending in part on the type ofsilane/borane agent used.

In some embodiments, the atomic percentage of titanium, or othersuitable metal, could be from about 10-30%, about 10-25%, or even about15-20%. In some embodiments, the atomic percentage of aluminum could begreater than about 15%, greater than about 20%, or even greater thanabout 25%. In some embodiments, the atomic percentage of silicon orboron could be greater than about 10%, greater than about 25%, orgreater than about 35%. In some embodiments, the atomic percentage ofcarbon could be less than about 40%, less than about 30%, or less thanabout 25%.

In some embodiments, a metal carbide film comprise, on an atomic basis,about 10-30% titanium, greater than about 15% aluminum, greater thanabout 10% silicon or boron, and less than about 40% carbon. In someembodiments, a metal carbide film comprise, on an atomic basis, about10-25% titanium, greater than about 20% aluminum, greater than about 25%silicon or boron, and less than about 30% carbon. In some embodiments, ametal carbide film comprise, on an atomic basis, about 15-20% titanium,greater than about 25% aluminum, greater than about 35% silicon orboron, and less than about 25% carbon.

In some embodiments, the atomic percentage of titanium, or othersuitable metal, could be from about 10-50%, about 15-45%, or even about20-40%. In some embodiments, the atomic percentage of aluminum could beless than about 15%, less than about 10%, or even less than about 5%,and in some cases below about 1%, such as about ˜0%. In someembodiments, the atomic percentage of silicon or boron could be greaterthan about 25%, greater than about 35%, or greater than about 45%. Insome embodiments, the atomic percentage of carbon could be less thanabout 20%, less than about 10%, or less than about 5%, and in some casesbelow about 1%, even about ˜0%.

In some embodiments, the total combined percentage of silicon, boron andaluminum in the film comprises more than about 20%, preferably more thanabout 30% and more preferably more than about 40% and, if desired, insome case more than about 45%.

A variety of compositions are possible. For example, in some embodimentsit may be desirable to fabricate a thin film having a composition whereonly one or some elements fall into any of the “preferable,” “morepreferable,” or “most preferable” ranges.

In some embodiments of the present disclosure, the disclosed depositionmethods can be used to form various stacks including, but not limitedto, NMOS stacks in the process of making a gate. For example, in someembodiments, NMOS stacks containing TiC thin films fabricated using themethods disclosed herein exhibit a leakage (J_(g)) (at −1V stress) ofless than about 10⁻² A/cm², less than about 10⁻³ A/cm², or less thanabout 3*10⁴ A/cm².

In some embodiments of the present disclosure, titanium carbide (TiC)films can be formed in dielectric/metal stack in which the equivalentoxide thickness, or EOT, of the stack can be less than about 1.3 nm,less than about 1.2 nm, preferably less than about 1.1 nm, or less thanabout 1.05 nm.

In some embodiments of the present disclosure, TiC films can be formedin which the effective workfunction, or eWF, can be from about 4.0 toabout 4.4 eV, from about 4.05 to about 4.35 eV, or from about 4.1 toabout 4.25 eV.

In some embodiments, the use of a silane/borane agent such as a silane(e.g., disilane or trisilane) can reduce the resistivity of a TiC thinfilm relative to a TiC film to which a silane/borane agent is notexposed. In some embodiments, the resistivity is reduced up to or asmuch as about 30%, up to or as much as about 40%, or up to or as much asabout 50%.

Use of a silane/borane agent as disclosed herein also has the potentialof providing a thin film, such as a TiC, with resistance to oxidation.In some embodiments, it is believed, without being held to any theory,that resistance to oxidation has been increased even when the films aresubjected to subsequent processing or the atmosphere. Without being tiedto any particular theory, it is believe that resistance to oxidation isreduced because the silane/borane agents tend to decrease the amount ofcarbon in the thin film as it is partially replaced by silicon or boronor some other element comprising the silane/borane agent.

Oxidation resistance is important because even a minor amount of oxygenin the stack could change the stack's electrical properties, namely eWF,making them unsuitable for intended purposes. Moreover, deposition ofthe stack without exposure to air or ambient moisture can be costly,difficult, and/or too complex. Thus, achieving the same or similarresults using a silane/borane agent greatly simplifies depositionprocess while also controlling costs.

Semiconductor Device Applications

Methods of fabricating semiconductor device structures will now bediscussed. Although described in terms of several specific contexts, oneof skill in the art will recognize that the processes described hereinare applicable to many other contexts as well.

The ALD processes disclosed herein may be successfully applied tofabricate NMOS transistors including planar devices as well as multiplegate transistors, such as FinFET.

Carbon-Containing Films as Electrodes

In some embodiments an electrode is formed by ALD of a conductive metalcarbide, such as TiC. With reference to FIG. 2, a layer of high-kdielectric material 200 is deposited onto a substrate (not shown). Thesubstrate may be treated prior to deposition of the high-k material. Forexample, in some embodiments, a thin interfacial layer (not shown) maybe deposited prior to deposition of the high-k material. In oneembodiment a thin chemical oxide or oxynitride is formed on the surface.In other embodiments a thermal oxide is grown on the substrate.

“High-k” generally refers to a dielectric material having a dielectricconstant (k) value greater than that of silicon oxide. Preferably, thehigh-k material has a dielectric constant greater than 5, morepreferably greater than about 10. Exemplary high-k materials include,without limitation, HfO₂, ZrO₂, Al₂O₃, TiO₂, Ta₂O₅, Sc₂O₃, lanthanideoxides and mixtures thereof, silicates and materials such as YSZ(yttria-stabilized zirconia), barium strontium titanate (BST), strontiumtitanate (ST), strontium bismuth tantalate (SBT) and bismuth tantalate(BT). Preferably, the high-k material is also deposited by an ALDprocess.

A layer or thin film 210 of a material such as TiN may be deposited overthe dielectric layer. Such a layer may act as an etch stop layer inwhich the etching has been previously performed in another reactor or ina other facility altogether. The transfer from one reactor or facilityto another can expose the thin films to contaminants such as water orair. The water or air generally oxidizes any exposed layer such as TiNtransforming the layer into essentially TiON. Such contamination caninterfere with the workfunction of the eventual stack.

A layer or thin film of conductive metal carbide 220, such as TiC, isdeposited over the layer 210 by ALD, as described above, to form theillustrated structure. It will be appreciated that in the illustratedembodiment the layers are not necessarily drawn to scale. The metalcarbide, thin layer of TiN, and underlying high-k material are patternedto form an electrode.

The metal carbide thin film 220 is preferably deposited over the thinfilm 210 by contacting the substrate with alternating pulses of a metalsource chemical, carbon source chemical and a silane/borane agent (notnecessarily in this order) or by depositing a complete metal carbidefilm by ALD and then treating the resulting film with a silane/boraneagent, as described above. The metal source chemical is preferably ahalide compound (e.g., TiCl₄) and the carbon source chemical ispreferably an organometallic compound, such as, e.g., trimethylaluminum(TMA).

In some embodiments, the thin layer of TiN is treated with asilane/borane agent. This can be done in addition to treating the metalcarbide film with a silane/borane agent or forming the metal carbidefilm utilizing a silane/borane agent. The silane/borane agent can reducethe thin film 210. If comprising TiON, a silane/borane agent reduces thethin film back to essentially TiN. In this manner the work function maybe improved or maintained as what it was before the oxidation occurred.And the presence of the silane/borane agent in the resulting carbidelayer can actually provide other benefits such as reduced resistivity.The silane/borane agent may be selected from the group including silanes(e.g., SiH₄, Si₂H₆, or Si₃H₈) and boranes (e.g., B₂H₆).

The thicknesses of the various layers in the stack may vary, though insome embodiments, such as the one illustrated in FIG. 2, layer 210 mayhave a thickness of about 10 Å to about 20 Å, preferably about 15 Å. Andlayer 220 may have a thickness generally greater than the thickness oflayer 210. The use of a protective treatment as presently disclosed canhave particular utility where the thicknesses of the various layers in astack, such as the one illustrated in FIG. 2, are reduced to achievesmaller electronic devices and circuitry. This is because thinner layersare more prone to oxygen diffusing through them. And, in someembodiments, the use of a silane/borane agent does not appreciablyincrease the overall thickness of the stack.

When forming the metal carbide film, unreacted source chemicals andreaction by-products are removed from the reaction chamber after eachsource chemical pulse, for example by evacuation and/or purging with aninert gas (e.g., N₂). In some embodiments, evacuation is achieved usinga vacuum pump or a plurality of vacuum pumps. The pulsing cycle, whichcan include a silane/borane agent in at least some cycles, is repeateduntil a metal carbide layer of the desired thickness has been formed. Insome embodiments, a silane/borane agent is also or only applied afterall the cycles have been completed. The silane/borane agent may beapplied either as a pulse or a soak. In some embodiments, it may bepreferably to apply the silane/borane agent as a soak after all thecycles have been completed. And preferably, the metal carbide layer hasa thickness between about 5 Å and about 1000 Å.

The conductive metal carbides deposited to form the electrode in theseembodiments are preferably selected from the group consisting of Ti, Zr,Hf, V, Nb, Ta, Cr, Mo, and W.

In some embodiments the metal carbide forms the electrode. In otherembodiments (not shown) another conductive material, such as a metal orpoly-Si, is deposited over the metal carbide. The additional conductivematerial may be deposited by ALD or by another deposition process, suchas by CVD or PVD. The deposition may be selective, or may be followed bypatterning steps. According to still another embodiment, annealing canbe performed after the metal carbide deposition. Suitable atmospheres,such as N₂ or forming gas (N₂/H₂) are apparent to skilled artisan.

Further processing steps, such as spacer deposition and source/drainimplantation, will be apparent to the skilled artisan.

Example 1 TiC Films

Using the methods disclosed here in, various titanium carbide thin filmswere deposited. The thin film was then analyzed using Rutherfordbackscattering spectrometry, or RBS, to determine the composition of thevarious films.

After analyzing the various films, it was determined that they thefollowing ranges of compositions on an atomic basis: about 17-20% Ti,about 17-27% Al, about 16-42% Si, and about 21-39% C.

Example 2 TiAlC and TiAlSiC in a Single Wafer Reactor

Titanium-aluminium carbide (TiAlC) and titanium-aluminum-carbide-silicon(TiAlSiC) thin films were deposited by Atomic layer deposition (ALD) inPulsar® 2000 R&D reactor using TiCl₄ as the titanium source andAl(CH₂CH₃)₃ as the aluminum and carbon source for the TiAlC films and inaddition disilane (Si₂H₆) or trisilane (Si₃H₈) was used as a siliconsource for TiAlSiC films.

TiAlC and TiAlSiC films were deposited using alternate and sequentialpulses of TiCl₄ and Al(CH₂CH₃)₃ and in the case of TiAlSiC filmsadditional alternate and sequential pulses of disilane (Si₂H₆) ortrisilane (Si₃H₈) were provided. TiAlC films were also soaked withdisilane (Si₂H₆) or trisilane (Si₃H₈) for about 1 minute. Films weredeposited and treated at a reaction temperature of about 415° C. TiCl₄was pulsed for 0.05 s and purged for 5 s. Al(CH₂CH₃)₃ was pulsed for 0.5s and purged for 5 s. Si₂H₆ or Si₃H₈ was pulsed for 0.5 s and purged for5 s. The Al(CH₂CH₃)₃ was heated to 60° C. and TiCl₄ was at roomtemperature. Carrier gas was ultrapure N₂ and the flow used was 0.6 slm.

Some of the films were deposited on thermal SiO₂/Si substrates whileothers were deposited on 2-3 nm HfO₂/0.4 nm SiO₂/Si substrate with orwithout a TiN intermediate layer (75 cycles) on top of a HfO₂ layer. TheTiN intermediate layer was deposited before TiAlC or TiAlSiC filmdeposition. Substrates having 2-3 nm HfO₂/0.4 nm SiO₂/Si and theoptionally deposited TiN intermediate layer were used to electricallycharacterize the films. Further another TiN layer (250 cycles) wasdeposited on top of the TiAlC or TiAlSiC layers. All TiN layers weredeposited using TiCl₄ and NH₃ as a precursors in the same reactionchamber in which TiAlC or TiAlSiC film deposition took place withoutmoving the substrate out of the reaction chamber. This resulted in astack structure of 6-8 nm TiN/3-4 nm TiAlSiC or TiAlC/(optional 2-2.5 nmTiN/) 2-3 nm HfO₂/0.4 nm SiO₂/Si measured by transmission electronmicroscopy (TEM) from the cross sectional area of the samples. Afterstack depositions, platinum dots were deposited by physical vapordeposition (PVD) on top of the samples, then the TiN, TiAlSiC, and TiAlClayers were etched away from the area between the platinum dots forminga capacitor array with circular top electrodes. These capacitorstructures were used to determine the effective work function of theTiAlSiC or TiAlC layer, the equivalent oxide thickness and the leakagecurrent density of the stacks, which represent important properties andquality of the films, although results from capacitor structures mightnot be directly comparable or transferrable to results of NMOStransistor structures.

The results and properties of the deposited TiAlC and TiAlSiC films areshown in Table 2. The growth rate of the deposited films ranged fromabout 2.55 to 3.8 Å/cycle on 20 nm thermal SiO₂/Si substrates and theresistivity ranged from 1300 to 3800 μΩcm. It may be noted that the soakwith disilane or trisilane formed a silicon layer on top of the TiAlClayer (though, the silane may also have penetrated or diffused through aportion o the TiAlC layer or even the whole layer); therefore the growthrate is not shown in the table. The films were measured by Rutherfordbackscattering spectroscopy (RBS) to find out elemental composition. Theeffective work functions (eWF) of the TiAlC and TiAlSiC layers rangedfrom 4.20 to 4.33 eV, the equivalent oxide thicknesses ranged from 1.04to 1.20, and the leakage current densities ranged from 5.17×10⁻³ A/cm²to 1.69×10⁻⁵ A/cm². Further it was assumed that the stability againstambient oxygen in air or oxidation or further (moisture and/or oxygen)might potentially have been increased, believed to be true without beingbound to any theory, due to reduced carbon content in TiAlSiC films.

The results achieved with the TiAlSiC films made with Si₃H₈, eitherincorporating Si₃H₈ into growth cycles or with subsequent soaking of thefilm, were the most desirable ones for end use in NMOS transistors, asthose had lowest effective work function and low resistivity while stillmaintaining reasonably low leakage and low EOT and potentially goodoxidation resistance. Also the TiAlSiC films made with Si₂H₆ eitherincorporating Si₂H₆ into growth cycles or with soaking are acceptable orbetter than the TiAlC films because of the increased oxidationresistance as explained above and the lower resistivity.

TABLE 2 Properties of TiAlC and TiAlSiC films. Growth rate ResistivityComposition Leakage at −1 V Film (Å/cycle) (μΩcm) (RBS) eWF (eV) EOT(nm) (A/cm²) TiAlC 3.14-3.80 3500-3800 Ti 18 at-%, 4.31-4.33 1.05-1.141.69 × 10⁻⁵-4.12 × 10⁻⁴ Al 38 at-%, C 42 at-%, H 2 at-%, TiAlSiC + Si₃H₈2.55-3.73 1300-1800 Ti 17 at-%, 4.20-4.28 1.11-1.20 1.01 × 10⁻⁴-5.17 ×10⁻³ Al 17-21 at-%, Si 26-42 at-%, C 21-34 at-%, H 1 at-%, Cl 0.5-1 at-%TiAlSiC + Si₂H₆ 3.20-3.80 1400-2500 Ti 17-20 at-%, 4.30 1.04 3.05 × 10⁻⁴Al 20-27 at-%, Si 16-24 at-%, C 35-39 at-%, H 1 at-%, Cl 0.5 at-%TiAlC + — — — 4.24-4.33 1.12-1.19 2.94 × 10⁻⁴-4.80 × 10⁻³ Si₃H₈ soak for60 s TiAlC + — — — 4.32 1.06 1.64 × 10⁻⁴ Si₂H₆ soak for 60 s

In all of the aforesaid embodiments, any element used in an embodimentcan interchangeably be used in another embodiment unless such areplacement is not feasible.

It will be understood by those of skill in the art that numerous andvarious modifications can be made without departing from the spirit ofthe present invention. Therefore, it should be clearly understood thatthe forms of the present invention are illustrative only and are notintended to limit the scope of the present invention. All modificationsand changes are intended to fall within the scope of the invention, asdefined by the appended claims.

1.-20. (canceled)
 21. A method of treating a nitride thin film on asubstrate to form a capping layer comprising silicon or boron, themethod comprising: exposing the nitride film to a silane compound or aborane compound, wherein the capping layer at least partially preventsfurther oxidation of the nitride thin film during subsequent processingor of films subsequently deposited over the treated film.
 22. The methodof claim 21, wherein the nitride thin film comprises a metal nitride.23. The method of claim 22, wherein the nitride thin film comprisestitanium nitride.
 24. The method of claim 21, wherein silicon or boronis incorporated into a portion of the nitride thin film to form thecapping layer.
 25. The method of claim 24, wherein the portion of thenitride thin film comprises a gradient of silicon or boron with agreater concentration of silicon or boron toward the top of the layer.26. The method of claim 21, wherein the capping layer is formed on thenitride thin film.
 27. The method of claim 21, wherein the capping layerthat is formed comprises a portion of the nitride thin film comprisingsilicon or boron as well as a layer comprising silicon or boron formedon the nitride layer.
 28. The method of claim 21, wherein the nitridethin film is exposed to the silane or borane compound for about 45seconds to about 180 seconds.
 29. The method of claim 21, wherein thecapping layer is less than about 3 nm thick.
 30. The method of claim 29,wherein the capping layer is less than about lmn thick.
 31. The methodof claim 21, wherein the nitride thin film is directly over andcontacting a metal carbide layer.
 32. The method of claim 21, whereinthe capping layer comprises more than about 20% silicon, boron, andaluminum, combined, on an atomic basis after exposing.
 33. The method ofclaim 21, wherein the silane or borane compound reduces oxidizedportions of the nitride thin film.
 34. The method of claim 21, whereinthe nitride thin film is exposed to silane or disilane.
 35. A method oftreating a titanium nitride thin film on a substrate to increaseoxidation resistance, the method comprising contacting the titaniumnitride film with a silane compound or a borane compound.
 36. The methodof claim 35, wherein silicon or boron is incorporated into a portion ofthe titanium nitride thin film.
 37. The method of claim 35, wherein acapping layer comprising silicon or boron is formed on the titaniumnitride thin film.
 38. The method of claim 35, wherein the titaniumnitride thin film is contacted with the silane or borane compound forabout 45 seconds to about 180 seconds.
 39. The method of claim 35,wherein the capping layer is less than about 3 nm thick.
 40. The methodof claim 35, wherein the silane compound or borane compound is selectedfrom the group consisting of monosilane, disilane, trisilane,organosilanes, borane, diborane, and organoboranes.